Flocculation in Estuaries: Modeling, Laboratory and In-situ Studies

Abstract

Modelling the flocculation of particles in a natural environment like an estuary is a challenging task owing to the complex particle-particle and particle-hydrodynamic interactions involved. In this chapter a summary is given of recent laboratory and in-situ studies regarding flocculation. A flocculation model is presented and the way to implement it in an existing sediment transport model is discussed. The model ought to be parametrized, which can be done by performing laboratory experiments which are reviewed. It is found, both from laboratory and in-situ studies, that flocculation between mineral sediment and organic matter is the dominant form of flocculation in estuarine systems. Mineral sediment in the water column is < 20 μm in size and its settling velocity is in the range [0–0.5] mm/s. Flocs can then be categorized in two types: flocs of size [20–200] μm and flocs of size > 200 μm. The origin of these two types is discussed. The two types of flocs are found at different positions in the water column and both have settling velocities in the range [0.5–10] mm/s.